Securities - Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 7,992,603	$ 11,822,584
Gross Unrealized Gains	269	261,198
Gross Unrealized Losses	(864,595)	(107,268)
Fair Value	7,128,277	11,976,514
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	764,650	69,551
Gross Unrealized Gains		374
Gross Unrealized Losses	(28,038)	(751)
Fair Value	736,612	69,174
U.S. Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	178,334	121,681
Gross Unrealized Gains		3,252
Gross Unrealized Losses	(6,675)	(1)
Fair Value	171,659	124,932
Mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,715,018	7,967,537
Gross Unrealized Gains	2	93,390
Gross Unrealized Losses	(605,452)	(95,872)
Fair Value	4,109,568	7,965,055
State and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,605,295	3,270,160
Gross Unrealized Gains	253	161,674
Gross Unrealized Losses	(179,009)	(9,146)
Fair Value	1,426,539	3,422,688
Corporates [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	401,912	316,840
Gross Unrealized Gains		2,504
Gross Unrealized Losses	(35,761)	(1,498)
Fair Value	366,151	317,846
Collateralized loan obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	327,394	76,815
Gross Unrealized Gains	14	4
Gross Unrealized Losses	(9,660)
Fair Value	$ 317,748	$ 76,819